OP0293 ANTI-CITRULLINATED HISTONE MONOCLONAL ANTIBODY CIT-013, A DUAL ACTION THERAPEUTIC FOR NEUTROPHIL EXTRACELLULAR TRAP ASSOCIATED AUTOIMMUNE DISEASES
Authors: M. Van der Linden, S. Kumari, D. Montizaan, S. Van Dalen, A. Kip, M. Foster, I. Reinieren, E. Neubert, L. Erpenbeck, T. Bruurmijn, P. Van Zandvoort, P. Vink, E. Meldrum, H. Van Es, R. Chirivi
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Neutrophil extracellular traps (NETs) contribute to the pathophysiology of multiple inflammatory and autoimmune diseases. Targeting the NETosis pathway has demonstrated significant therapeutic potency in various disease models (Chirivi <i>et al</i>., 2021). Here we describe a first in class monoclonal antibody (CIT-013) with high affinity for citrullinated histones H2A and H4 which inhibits NETosis and reduces tissue NET burden <i>in vivo</i> with significant anti-inflammatory consequences. CIT-013 is currently in phase 1 clinical trials with phase 2a studies in RA due to commence in 2024. <h3>Objectives</h3> The objective of the current study was to further unravel CIT-013's mode of action. Questions which we wanted to answer are: 1) How and when does CIT-013 interfere with the NETosis pathway?, and 2) what is the faith of CIT-013 opsonized NETs and netting neutrophils? Furthermore, we investigated whether CIT-013's epitope is expressed in rheumatoid arthritis (RA) synovial tissue. <h3>Methods</h3> <i>In vitro</i> life imaging studies using neutrophils and macrophages in combination with monovalent as well as bivalent CIT-013 have been performed to investigate CIT-013's mode of action. An <i>in vivo</i> lung inflammation mouse model was used to investigate CIT-013's effect on NET burden as well as phagocytic macrophages. Finally, the presence of CIT-013's epitope in human RA synovial tissues was investigated using immunohistochemistry techniques. <h3>Results</h3> Detection of CIT-013 epitopes in RA synovium provides evidence that RA is an autoimmune disease with excessive citrullinated-NETs that can be targeted by CIT-013. We show that CIT-013 acts upon the final stage of NETosis, binding to its chromatin epitopes when plasma membrane integrity is compromised to prevent NET release. Bivalency of CIT-013 is necessary for NETosis inhibition. In addition, we show that CIT-013 binding to NETs and netting neutrophils enhances their phagocytosis by macrophages. Furthermore, we demonstrate that a mouse variant of CIT-013 reduces tissue NET burden <i>in vivo</i> at least in part through enhanced macrophage phagocytosis. <h3>Conclusion</h3> Since NETs contribute to the pathophysiology of many immune mediated inflammatory diseases, including autoimmune diseases such as RA, CIT-013's unique ability to both inhibit NET release and enhance NET clearance indicates the importance of this first in class therapeutic antibody as a new emerging therapy. <h3>Reference</h3> [1]Chirivi et al,. Cellular &amp; Molecular Immunology 18: p1528-1554, 2021. DOI: 10.1038/s41423-020-0381-3 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Maarten van der Linden Shareholder of: Stock options, Employee of: Employee of Citryll, Sangeeta Kumari Shareholder of: Stock options, Employee of: Employee of Citryll, Daphne Montizaan Shareholder of: Stock options, Employee of: Employee of Citryll, Stephanie van Dalen Shareholder of: Stock options, Employee of: Employee of Citryll, Annemarie Kip Shareholder of: Stock options, Employee of: Employee of Citryll, Martyn Foster: None declared, Inge Reinieren Employee of: Past employee of Citryll, Elsa Neubert: None declared, Luise Erpenbeck: None declared, Tirza Bruurmijn Shareholder of: Stock options, Employee of: Employee of Citryll, Peter van Zandvoort Shareholder of: Stock options, Employee of: Employee of Citryll, Paul Vink Employee of: Former employee of Citryll, Eric Meldrum Shareholder of: Stock options, Employee of: Employee of Citryll, Helmuth van Es Shareholder of: Stock options and shares, Employee of: Employee of Citryll, Renato Chirivi Shareholder of: Stock options and shares, Employee of: Employee of Citryll.